In a digital communication system, the Moving Picture Experts Groups 2 (MPEG-2) transport stream standard is a detail specification with respect to compression solutions and system layers in various types of applications of standard definition TV (SDTV) and high definition TV (HDTV). In the MPEG-2 standard, in order to combine one or more audio streams, video streams or other basic data streams to a single or a plurality of data streams that are more adaptive to store or transmit, the streams need to be repacked and re-encoded. Moreover, various time marks, information of system control, and the like, are inserted in a transport stream, which is then transmitted to a channel encoder and a modulator. At a broadcasting transmitting end, the video streams, the audio streams and the data information streams are combined to a single transport stream to be modulated and transmitted through an air medium via electric waves. At a receiving end, a received digital modulated signal is demodulated in order to restore the original transport stream; later on, the original transport stream is segmented and parsed to images, voices and other information, so as to display images of programs on a monitor, for example.
FIG. 1 is a schematic diagram of a Digital Video Broadcasting (DVB) system. A transmitter 150 comprises an encoder 100 and a modulator 110, and a receiver 160 comprises a demodulator 120 and a decoder 130. The DVB system is inputted with one or a plurality of digital data streams, each of which is transmitted via a physical layer pipe (PLP) in the form of packet of 188 bytes. In a European DVB-T2 system, encoded transport streams TS0, TS1 and TS2 represent different program channels. Modulator 110 divides these encoded transport streams into data streams named data_PLP0, data_PLP1, data_PLP2, and a data stream named common_PLP. Data stream common_PLP contains common data packets commonly contained in the transport streams TS0, TS1 and TS2. Except for the common data packets and null packets, the data stream data_PLP0, data_PLP1 and data_PLP2 are data packets in the transport stream TS0, TS1 and TS2, respectively. Combining all the common data packets from different data streams as one data packet common_PLP for transmitting saves bandwidth occupied by repetitive transmission of the same data packets. A desired channel to be viewed is selected at the receiving end, e.g., the selected channel corresponds to the transport stream TS0. Accordingly, the demodulator 120 in the receiver 160 combines the data stream data_PLP0 corresponding to the transport stream TS0 with the data stream common_PLP, so as to reconstruct a transport stream TS0' compliant to the MPEG-2 specifications to the decoder 130. Therefore, in response to the DVB-T2 standards, an apparatus and a method capable of accurately reconstructing a transport stream as well as obtaining its output bit rate are in need.